The pathogenesis of herpesvirus infections in man and in experimental animals are investigated by characterization of viral isolates and examination of humoral and cell-mediated immune responses. Development of immune adherence hemagglutination (IAHA) techniques provides a practical and sensitive method to detect antibody to herpes simplex (HSV) and varicella zoster (V-Z) viruses. Absence of IAHA antibody is associated with increased risk of dissemination of herpes zoster infection. The efficacy and mechanism of action of antiviral compounds are examined in clinical trials, as well as in vitro. One such compound, ara-A, appears to decrease mortality in herpes simplex encephalitis and accelerates resolutions of skin lesions in varicella infections in the immunosuppressed. Additional trials in V-Z and HSV infections are currently underway. BIBLIOGRAPHIC REFERENCES: Ch'ien, L. T., Whitley, R. J., Alford, C. A., Galasso, G. J., and Dolin, R.: NIAID Collaborative Antiviral Study - Preliminary results with ara-A therapy of herpes zoster in the immunosuppressed. J. Infect. Dis. 133: A184-A189, 1976. Coker-Vann, M. and Dolin, R.: Effect of adenine-arabinoside on Epstein-Barr virus in vitro. J. Infect. Dis. 135: 447-453, 1977.